Siftproof bag and method of making the same



May 10, 1932. FREYDBERG 1,857,949

SIFTPROOF BAG AND METHOD OF MAKING THE SAME Filed Jan. 16, 1931 I N V EN TOR. 52/ f2: aaaee A TTORNEYS.

Patented May 10, 1932 UNITED STATES PATENT OFFICE I ELI FBEYDBEBG, 01 NEW YOBKQN. Y ASSIGNOR TO FREYDBEBG BROS. INC, 0! NEW YORK, N. Y., A CORPORATION OF NEW YORK SIFTPBOOF BAG AND METHOD OF MAKING sum Application filed January 16, 1931. Serial No. 509,242.

or closure due to the fact that the finely pow-.

dered material will sift through very fine openings at points where the adhesive reinforcements are not tightly secured to the surface of the bag due either to manufacturing defects or to loosening during handling of the packages which are usually quite heavy. To cure this defect and to strengthen the bags they are generally provided with a reinforcing strip which is stitched to the ha and even under this construction the very e materials of the character above mentioned will sift through the holes made by the needle and threads. I

I am aware that several proposals have been made for bags which will be sift-proof or weather and water proof. Such proposals have recommended the use of alternate layers of fabric and paper adhesively secured together, and also the provision of a fabric strip at certain points on the paper bag to permit of stitching, the stitching to be covered by a supplementary paper flap adhesively secured to the ba These constructions are impractical an costly and none 0 the bags known heretofore have afforded a practical and satisfactory sift-proof container of the character above mentioned and for the purposes specified.

Accordin to my invention a paper or fibrous bag w ich is sift-proof and very strong may be produced at substantially the same cost as existing bags, as the invention contemplates the application of a solution or liquid of such a character along the stitching that it will fill the holes and form a film on the surface and over the stitches and holes when hardened and yet retain sufiicient flexf quantity.

ibility to permit rough usage of the bags wlthout the film cracking or pulling away from the surface and holes which it covers and fills.

Another object of the invention is to provide means for applying the film to the bags during the stitching operation with no noticeable mcrease in cost due to additional labor.

The foregoing and other objects of the invention will he specifically referred to and pointed out during the course of the detailed description which is to be read in connection with the accompanying drawings showing an embodiment of the invention, in which Fig. 1 is a perspective view of a bag embodying the invention.

Fig. 2 is a sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a side elevation of apparatus for carrying out the invention; and v Fig. 4 is an enlarged detail view of an instrumentality embodied in Fig. 3.

In the accompanying drawings numeral 10 designates a paper bag of known and standard construction having the reinforcing strips 11 of crinkle or other tough paper sewn along its ends and provided with a filling spout 12 at one corner. This bag is shown merely for the purpose of illustration as it is very practical in connection with the packing-of cement and heavy. powdered materials, but it will be understood after a full reading of the following description that the invention can be readily applied to any other type of paper bag designed for use in packing finely powdered materials in considerable W'hen the stitches 13 are applied to the bag along the reinforcing strip'll, the needle and thread'necessarily makes a number of holes 14 which are not com letely filled by the thread and through whic the finely powdered material will sift during handling of the bags. I provide a coating 15 of liquid which can heap lied at normal temperatures and which will flow into the holes and firmly adhere to the surface along the stitches to completely cover the surface and completely close the bag against leakage. As has been mentioned this liquid when hardene dlOO baseandaso will retain suflicient flexibility to permit filling of the bag and normal rough handling thereof without any leakage whatever. I have found in actual practice and by tests that a solution composed of a cellulose base and a solvent, for example pyroxylin, when applied along the stitches accomplishes the purposes above stated. A large paper bag of the ty e illustrated andcompletely filled with finely powdered lime was tested by abnormal as well as normal handling. That is, the bag was thrown around and struck heavy blows for quite some time without any dust or lime appearin through the bag and only when a portion 0 the bag between the seams at a non-reinforced point broke was there any leakage. The sealing was found to be complete and entirely flexible.

An economical and efiicacious manner of applying the solution along the seams is i1 ustrated in Fig. 3 showing the stitching elements 16 of a sewing machine mounted on atable 17 in advance of the spout 18. As the bag progresses along the table beneath the needle during the stitching operation, the seam passes beneath the spout which is connected to a reservoir, 19, containing the solution. The spout includes as a spreader the blade 20 shown as of flat construction and provided with a groove 21 through which the stitches, which are slightly elevated above the surface of the bag pass. The spout may be so constructed as to provide two passages and spreader blades so. spaced as to engage opposite sides of the bag and thus apply the solution to both sides'of the seam during the stitching operation, or only one spout and spreader may be used to apply the solution to one side during the stitching operation and the solution applied to the other side afterwards.

I have found that pyroxylin, a solution composed of a cellulose base and solvent is highly efficient and practical. In the-first place it can be readily applied in numerous ways and at normal temperature and when so applied completely fills the holes, secondly it hardens quickly but retains flexibility indefinitely-so that it will not crack and fall away from the holes and surfaces, but will remain as a coating completely covering the holes and surfaces regardless of temperature and climatic conditions and handling of the bags. I have found these qualities completely lacking in other substances such as wax-or paraflin, which must be applied by dipping the bag in a molten mass or pouring the melted wax or parafiin at abnormal temperatures. When such substances have hardened they crack when the bag is filled and fall a'way during handling of the filled bag leaving the holes or some of them open. A solution or 1i uid composed of a cellulose vent, however, is not subject to these difiiculties as it is highly adhesive, flexible and applied with facility.

I claim:

1. A bag having one end closed by a line of stitches, and means for closing the openin 's formed by the stitches to render the bag si t-proof, which consists in coating the stitches with a water repellent composition including a solvent adapted to be applied at normal temperature in fluent form, said composition when dry being freely flexible with and adherent to the surfaces to which applied during filling of the bag andhandling of the filled bag.

2. A bag having one end closed by a line of stitches, and means for closing the openin s formed by the stitches to render the bag sittproof, said means comprising a coating of pyroxylin and a solvent applied in fluent form and which when dried adheres to the surface to which it is applied in the form of a flexible film over the line of stitches and openings formed thereby.

3. A bag having an end closed by a line of stitches, an dmeans for sealing the openings formed in the bag by the stitches, said means comprising a coating including a cellulose base and a solvent applied'along the line of stitches over said. openings in fluent form at normal temperature and which when dried adheres'to the surface to which applied and forms thereon and over said openings a water repellent film having retentive flexible and adherent qualities."

4. A sift-proof bag of the character described having at least one end closed by a reinforcing strip, stitches through the reinforcing strip and bag securing the same together, and a coating on said. strip over said stitches and openings formed thereby, said coating comprising a cellulose solution applied at normal temperature in liquid form along said line of stitches and which when dried adheres to the surface of the strip formlng a flexible film over the stitches and holes, said coating being freely flexible with the strl and bag during filling and handling of the ag without cracking ofi'.

Signed at New York city in the county of New York and State of New York this 9th day of January A. D. 1931.

- ELI FREYDBERG. 

